Paramount and Warner Bros. have signed David Fincher to direct a pair of tentpoles — “Zodiac,” starring Mark Ruffalo, and “The Curious Case of Benjamin Button,” with Brad Pitt and Cate Blanchett — back-to-back.

Fincher, whose last film was 2002’s “Panic Room,” is in pre-production on “Zodiac,” which also stars Robert Downey Jr., Jake Gyllenhaal and Anthony Edwards. Production is slated to start in September, with Jamie Vanderbilt adapting from Robert Graysmith’s “Zodiac” and 2002 sequel “Zodiac Unmasked: The Identity of America’s Most Elusive Serial Killer Revealed.”

Fincher and partner Cean Chaffin are producing with Vanderbilt and Phoenix principals Mike Medavoy, Arnold Messer and Brad Fischer.

Shooting will take place in San Francisco — where the Zodiac Killer operated starting in the late 1960s — and in Los Angeles.

Warner is taking the lead on producing “Zodiac.” Par will handle domestic distribution while Warner will handle international.

Par and Warner are aiming for Fincher to start lensing “Benjamin Button” in October 2006. Pitt and Blanchett currently are starring in Paramount’s “Babel” for helmer Alejandro Gonzalez Inarritu.

“Benjamin Button” will mark the third time Pitt has teamed with Fincher following “Seven” and “Fight Club.”

“Benjamin Button” is produced by Kathleen Kennedy and Frank Marshall with a script by Eric Roth, who won an Oscar for penning “Forrest Gump.

” Fitzgerald’s story “The Curious Case of Benjamin Button” centers on a man who, at age 50, begins aging backward and the complications that ensue when he falls in love with a woman of 30.

The story’s been set in New Orleans, allowing the studios to take advantage of Louisiana’s production incentives.

“Benjamin Button” has been in development for well over a decade, previously with Rastar and Imagine. At various times, Spike Jonze and Gary Ross have been attached to direct; writers have included Jim Taylor, Robin Swicord and Charlie Kaufman.

Paramount is taking the lead on “Button” and handling domestic distribution; Warner will market the pic in foreign territories.

Fincher had been attached to direct “Mission: Impossible 3” and “The Lords of Dogtown” before settling on “Zodiac” and “Benjamin Button.”